/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.expr.nodevalue;

import static javax.xml.datatype.DatatypeConstants.*;
import static org.apache.jena.sparql.expr.nodevalue.NumericType.OP_DECIMAL;
import static org.apache.jena.sparql.expr.nodevalue.NumericType.OP_DOUBLE;
import static org.apache.jena.sparql.expr.nodevalue.NumericType.OP_FLOAT;
import static org.apache.jena.sparql.expr.nodevalue.NumericType.OP_INTEGER;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.Normalizer;
import java.text.NumberFormat;
import java.time.ZonedDateTime;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import javax.xml.datatype.DatatypeConstants;
import javax.xml.datatype.Duration;
import javax.xml.datatype.XMLGregorianCalendar;

import org.apache.jena.atlas.lib.IRILib;
import org.apache.jena.atlas.lib.StrUtils;
import org.apache.jena.datatypes.RDFDatatype;
import org.apache.jena.datatypes.xsd.XSDDatatype;
import org.apache.jena.graph.Node;
import org.apache.jena.graph.NodeFactory;
import org.apache.jena.rdf.model.impl.Util;
import org.apache.jena.sparql.ARQInternalErrorException;
import org.apache.jena.sparql.SystemARQ;
import org.apache.jena.sparql.expr.*;
import org.apache.jena.sparql.util.DateTimeStruct;
import org.apache.jena.sparql.util.XSDNumUtils;
/**
 * Implementation of XQuery/XPath functions and operators.
 * http://www.w3.org/TR/xpath-functions/
 * <p>
 * See also {@link XSDNumUtils}.
 */
public class XSDFuncOp
{
    private XSDFuncOp() {}

    // The choice of "24" is arbitrary but more than 18 (XSD 1.0) or 16 (XSD 1.1) as required by F&O
    //   F&O 3.1: section 4.2 (end intro)
    //   https://www.w3.org/TR/xpath-functions/#op.numeric section 4.2
    private static final int DIVIDE_PRECISION = 24;
    // --------------------------------
    // Numeric operations
    // http://www.w3.org/TR/xpath-functions/#op.numeric
    // http://www.w3.org/TR/xpath-functions/#comp.numeric

    public static NodeValue numAdd(NodeValue nv1, NodeValue nv2) {
        switch (classifyNumeric("add", nv1, nv2)) {
            case OP_INTEGER :
                return NodeValue.makeInteger(nv1.getInteger().add(nv2.getInteger()));
            case OP_DECIMAL :
                return NodeValue.makeDecimal(nv1.getDecimal().add(nv2.getDecimal()));
            case OP_FLOAT :
                return NodeValue.makeFloat(nv1.getFloat() + nv2.getFloat());
            case OP_DOUBLE :
                return NodeValue.makeDouble(nv1.getDouble() + nv2.getDouble());
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    public static NodeValue numSubtract(NodeValue nv1, NodeValue nv2) {
        switch (classifyNumeric("subtract", nv1, nv2)) {
            case OP_INTEGER :
                return NodeValue.makeInteger(nv1.getInteger().subtract(nv2.getInteger()));
            case OP_DECIMAL :
                return NodeValue.makeDecimal(nv1.getDecimal().subtract(nv2.getDecimal()));
            case OP_FLOAT :
                return NodeValue.makeFloat(nv1.getFloat() - nv2.getFloat());
            case OP_DOUBLE :
                return NodeValue.makeDouble(nv1.getDouble() - nv2.getDouble());
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    public static NodeValue numMultiply(NodeValue nv1, NodeValue nv2) {
        switch (classifyNumeric("multiply", nv1, nv2)) {
            case OP_INTEGER :
                return NodeValue.makeInteger(nv1.getInteger().multiply(nv2.getInteger()));
            case OP_DECIMAL :
                return NodeValue.makeDecimal(nv1.getDecimal().multiply(nv2.getDecimal()));
            case OP_FLOAT :
                return NodeValue.makeFloat(nv1.getFloat() * nv2.getFloat());
            case OP_DOUBLE :
                return NodeValue.makeDouble(nv1.getDouble() * nv2.getDouble());
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    /* Quote from XQuery/XPath F&O:
        For xs:float or xs:double values, a positive number divided by positive zero returns INF.
        A negative number divided by positive zero returns -INF.
        Division by negative zero returns -INF and INF, respectively.
        Positive or negative zero divided by positive or negative zero returns NaN.
        Also, INF or -INF divided by INF or -INF returns NaN.
     */

    public static NodeValue numDivide(NodeValue nv1, NodeValue nv2) {
        switch (classifyNumeric("divide", nv1, nv2)) {
            case OP_INTEGER : {
                // Note: result is a decimal
                BigDecimal d1 = new BigDecimal(nv1.getInteger());
                BigDecimal d2 = new BigDecimal(nv2.getInteger());
                return decimalDivide(d1, d2);
            }
            case OP_DECIMAL : {
                BigDecimal d1 = nv1.getDecimal();
                BigDecimal d2 = nv2.getDecimal();
                return decimalDivide(d1, d2);
            }
            case OP_FLOAT :
                // No need to check for divide by zero
                return NodeValue.makeFloat(nv1.getFloat() / nv2.getFloat());
            case OP_DOUBLE :
                // No need to check for divide by zero
                return NodeValue.makeDouble(nv1.getDouble() / nv2.getDouble());
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    private static NodeValue decimalDivide(BigDecimal d1, BigDecimal d2) {
        if ( d2.equals(BigDecimal.ZERO) )
            throw new ExprEvalException("Divide by zero in decimal divide");
        BigDecimal d3;
        try {
            // Jena 3.16.0 used d1.divide(d2, DIVIDE_PRECISION, BigDecimal.ROUND_FLOOR)
            // which can looses precision even when there is exact answer.
            // See JENA-1943 and JENA-2116
            // Casting the dividend (the left hand value) to xsd:double gets approximate division always.

            // Exact where possible.
            // But this generates an exception when not exact which can be costly in some situations.
            d3 = d1.divide(d2, MathContext.UNLIMITED);
        } catch (ArithmeticException ex) {
            d3 = d1.divide(d2, DIVIDE_PRECISION, RoundingMode.HALF_EVEN);
        }
        return NodeValue.makeDecimal(d3);
    }

    /** Integer divide */
    public static NodeValue numIntegerDivide(NodeValue nv1, NodeValue nv2) {
        switch (XSDFuncOp.classifyNumeric("idiv", nv1, nv2)) {
            case OP_INTEGER :
                BigInteger bi1 = nv1.getInteger();
                BigInteger bi2 = nv2.getInteger();
                if ( BigInteger.ZERO.equals(bi2) )
                    throw new ExprEvalException("Divide by zero in IDIV");
                BigInteger bi3 = bi1.divide(bi2);
                return NodeValue.makeInteger(bi3);
            case OP_DECIMAL :
                BigDecimal bd_a = nv1.getDecimal();
                BigDecimal bd_b = nv2.getDecimal();
                if ( BigDecimal.ZERO.compareTo(bd_b) == 0 )
                    throw new ExprEvalException("Divide by zero in IDIV");
                BigInteger bi = bd_a.divideToIntegralValue(bd_b).toBigIntegerExact();
                return NodeValue.makeInteger(bi);
            case OP_FLOAT : {
                float arg1 = nv1.getFloat();
                float arg2 = nv2.getFloat();
                if ( arg2 == 0.0  )
                    throw new ExprEvalException("Divide by zero in IDIV");
                if ( Float.isNaN(arg1) || Float.isNaN(arg2) )
                    throw new ExprEvalException("Divide by NaN in IDIV");
                if ( Float.isInfinite(arg1) )
                    throw new ExprEvalException("+/-INF in IDIV");
                float f = arg1 / arg2;
                return NodeValue.makeInteger((long)f);
            }
            case OP_DOUBLE : {
                double arg1 = nv1.getDouble();
                double arg2 = nv2.getDouble();
                if ( arg2 == 0.0  )
                    throw new ExprEvalException("Divide by zero in IDIV");
                if ( Double.isNaN(arg1) || Double.isNaN(arg2) )
                    throw new ExprEvalException("Divide by NaN in IDIV");
                if ( Double.isInfinite(arg1) )
                    throw new ExprEvalException("+/-INF in IDIV");
                double d = arg1 / arg2;
                return NodeValue.makeInteger((long)d);
            }
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    public static NodeValue numericMod(NodeValue nv1, NodeValue nv2) {
        // F&O modulus operation != Java Number.mod operations.
        switch (XSDFuncOp.classifyNumeric("mod", nv1, nv2)) {
            // a = (a idiv b)*b+(a mod b)
            // => except corner cases (none or xsd:decimal except precision?)
            // a - (a idiv b)*b

            case OP_INTEGER :
                // Not BigInteger.mod. F&O != Java.
                BigInteger bi1 = nv1.getInteger();
                BigInteger bi2 = nv2.getInteger();
                if ( BigInteger.ZERO.equals(bi2) )
                    throw new ExprEvalException("Divide by zero in MOD");
                BigInteger bi3 = bi1.remainder(bi2);
                return NodeValue.makeInteger(bi3);
            case OP_DECIMAL :
                BigDecimal bd_a = nv1.getDecimal();
                BigDecimal bd_b = nv2.getDecimal();
                if ( BigDecimal.ZERO.compareTo(bd_b) == 0 )
                    throw new ExprEvalException("Divide by zero in MOD");
                // This is the MOD for X&O
                BigDecimal bd_mod = bd_a.remainder(bd_b);
                return NodeValue.makeDecimal(bd_mod);
            case OP_FLOAT :
                float f1 = nv1.getFloat();
                float f2 = nv2.getFloat();
                if ( f2 == 0 )
                    throw new ExprEvalException("Divide by zero in MOD");
                return NodeValue.makeFloat( f1 % f2);
            case OP_DOUBLE :
                double d1 = nv1.getDouble();
                double d2 = nv2.getDouble();
                if ( d2 == 0 )
                    throw new ExprEvalException("Divide by zero in MOD");
                return NodeValue.makeDouble(d1 % d2);
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    public static NodeValue max(NodeValue nv1, NodeValue nv2) {
        int x = compareNumeric(nv1, nv2);
        if ( x == Expr.CMP_LESS )
            return nv2;
        return nv1;
    }

    public static NodeValue min(NodeValue nv1, NodeValue nv2) {
        int x = compareNumeric(nv1, nv2);
        if ( x == Expr.CMP_GREATER )
            return nv2;
        return nv1;
    }

    /** {@literal F&O} fn:not */
    public static NodeValue not(NodeValue nv) {
        boolean b = XSDFuncOp.effectiveBooleanValue(nv);
        return NodeValue.booleanReturn(!b);
    }

    /** {@literal F&O} fn:boolean */
    public static NodeValue effectiveBooleanValueAsNodeValue(NodeValue nv) {
        if ( nv.isBoolean() ) // "Optimization" (saves on object churn)
            return nv;
        return NodeValue.booleanReturn(effectiveBooleanValue(nv));
    }

    /** Effective Boolean Value */
    public static boolean effectiveBooleanValue(NodeValue nv) {
        Objects.requireNonNull(nv, "NodeValue is null in call to effectiveBooleanValue");

        // Apply the "boolean effective value" rules
        // boolean: value of the boolean (strictly, if derived from xsd:boolean)
        // string literal: lexical form is not the empty string.
        // numeric: number != NaN && number != 0
        // http://www.w3.org/TR/sparql12-query#ebv
        // http://www.w3.org/TR/xquery/#dt-ebv

        if ( nv.isBoolean() )
            return nv.getBoolean();
        if ( nv.isString() || nv.isLangString() )
            // String
            return ! nv.getString().isEmpty();
        if ( nv.isInteger() )
            return !nv.getInteger().equals(BigInteger.ZERO);
        if ( nv.isDecimal() ) {
            // Not equals(BigDecimal.ZERO) which is only scale=0
            return nv.getDecimal().signum() != 0;
        }
        if ( nv.isDouble() ) {
            double v = nv.getDouble();
            return v != 0.0d && ! Double.isNaN(v);
        }
        if ( nv.isFloat() ) {
            float v = nv.getFloat();
            return v != 0.0f && ! Float.isNaN(v);
        }
        NodeValue.raise(new ExprEvalException("Not a boolean effective value (wrong type): " + nv));
        // Does not return
        return false;
    }

    public static NodeValue unaryMinus(NodeValue nv) {
        switch (classifyNumeric("unaryMinus", nv)) {
            case OP_INTEGER :
                return NodeValue.makeInteger(nv.getInteger().negate());
            case OP_DECIMAL :
                return NodeValue.makeDecimal(nv.getDecimal().negate());
            case OP_FLOAT :
                return NodeValue.makeFloat(-nv.getFloat());
            case OP_DOUBLE :
                return NodeValue.makeDouble(-nv.getDouble());
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : " + nv);
        }
    }

    public static NodeValue unaryPlus(NodeValue nv) {
        // Not quite a no-op - tests for a number
        NumericType opType = classifyNumeric("unaryPlus", nv);
        return nv;
    }

    public static NodeValue abs(NodeValue nv) {
        switch (classifyNumeric("abs", nv)) {
            case OP_INTEGER :
                return NodeValue.makeInteger(nv.getInteger().abs());
            case OP_DECIMAL :
                return NodeValue.makeDecimal(nv.getDecimal().abs());
            case OP_FLOAT :
                return NodeValue.makeFloat(Math.abs(nv.getFloat()));
            case OP_DOUBLE :
                return NodeValue.makeDouble(Math.abs(nv.getDouble()));
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : " + nv);
        }
    }

    public static NodeValue ceiling(NodeValue v) {
        switch (classifyNumeric("ceiling", v)) {
            case OP_INTEGER :
                return v;
            case OP_DECIMAL :
                BigDecimal dec = v.getDecimal().setScale(0, RoundingMode.CEILING);
                return NodeValue.makeDecimal(dec);
            case OP_FLOAT :
                return NodeValue.makeFloat((float)Math.ceil(v.getFloat()));
            case OP_DOUBLE :
                return NodeValue.makeDouble(Math.ceil(v.getDouble()));
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : " + v);
        }
    }

    public static NodeValue floor(NodeValue v) {
        switch (classifyNumeric("floor", v)) {
            case OP_INTEGER :
                return v;
            case OP_DECIMAL :
                BigDecimal dec = v.getDecimal().setScale(0, RoundingMode.FLOOR);
                return NodeValue.makeDecimal(dec);
            case OP_FLOAT :
                return NodeValue.makeFloat((float)Math.floor(v.getFloat()));
            case OP_DOUBLE :
                return NodeValue.makeDouble(Math.floor(v.getDouble()));
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : " + v);
        }
    }

    public static NodeValue round(NodeValue v) {
        switch (classifyNumeric("round", v)) {
            case OP_INTEGER:
                return v;
            case OP_DECIMAL:
                int sgn = v.getDecimal().signum();
                BigDecimal dec;
                if (sgn < 0)
                    dec = v.getDecimal().setScale(0, RoundingMode.HALF_DOWN);
                else
                    dec = v.getDecimal().setScale(0, RoundingMode.HALF_UP);
                return NodeValue.makeDecimal(dec);
            case OP_FLOAT:
                return NodeValue.makeFloat(Math.round(v.getFloat()));
            case OP_DOUBLE:
                return NodeValue.makeDouble(Math.round(v.getDouble()));
            default:
                throw new ARQInternalErrorException("Unrecognized numeric operation : " + v);
        }
    }

    // The following function 'roundXpath3' implements the definition for "fn:round" in F&O v3.
    // This is different to the "fn:round" in F&O v2.
    // SPARQL 1.1 references F&O v2.
    private static BigDecimal roundDecimalValue(BigDecimal dec, int precision, boolean isHalfToEven)
    {
        if(isHalfToEven){
            return dec.setScale(precision, RoundingMode.HALF_EVEN);
        }
        else {
            int sgn = dec.signum();
            if (sgn < 0)
                return dec.setScale(precision, RoundingMode.HALF_DOWN);
            else
                return dec.setScale(precision, RoundingMode.HALF_UP);
        }
    }

    public static NodeValue roundXpath3(NodeValue v, NodeValue precision, boolean isHalfEven) {
        if(!precision.isInteger()){
            throw new ExprEvalTypeException("The precision for rounding should be an integer");
        }
        int precisionInt = precision.getInteger().intValue();
        String fName = isHalfEven ? "round-half-to-even" : "round";
        switch (classifyNumeric(fName, v)) {
            case OP_INTEGER :
                BigDecimal decFromInt = roundDecimalValue(new BigDecimal(v.getInteger()),precisionInt,isHalfEven);
                return NodeValue.makeInteger(decFromInt.toBigIntegerExact());
            case OP_DECIMAL :
                return NodeValue.makeDecimal(roundDecimalValue(v.getDecimal(),precisionInt,isHalfEven));
            case OP_FLOAT :
                BigDecimal decFromFloat = roundDecimalValue(new BigDecimal(v.getFloat()),precisionInt,isHalfEven);
                return NodeValue.makeFloat(decFromFloat.floatValue());
            case OP_DOUBLE :
                BigDecimal decFromDouble = roundDecimalValue(new BigDecimal(v.getDouble()),precisionInt,isHalfEven);
                return NodeValue.makeDouble(decFromDouble.doubleValue());
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : " + v);
        }
    }

    public static NodeValue sqrt(NodeValue v) {
        return NodeValue.makeDouble(Math.sqrt(v.getDouble()));
    }

    // NB Java string start from zero and uses start/end
    // F&O strings start from one and uses start/length

    public static NodeValue javaSubstring(NodeValue v1, NodeValue v2) {
        return javaSubstring(v1, v2, null);
    }

    public static NodeValue javaSubstring(NodeValue nvString, NodeValue nvStart, NodeValue nvFinish) {
        try {
            String string = nvString.getString();
            int start = nvStart.getInteger().intValue();
            if ( nvFinish == null )
                return NodeValue.makeString(string.substring(start));

            int finish = nvFinish.getInteger().intValue();
            return NodeValue.makeString(string.substring(start, string.offsetByCodePoints(start, finish - start)));
        } catch (IndexOutOfBoundsException ex) {
            throw new ExprEvalException("IndexOutOfBounds", ex);
        }
    }

    // expecting nvString = format | nvStart = value (int,float, string,....)
    public static NodeValue javaSprintf(NodeValue nvFormat, List<NodeValue> valuesToPrint) {
        try {
            String formatForOutput = nvFormat.getString();
            List<Object> objVals = new ArrayList<>();
            for(NodeValue nvValue:valuesToPrint) {
                ValueSpace vlSpClass = nvValue.getValueSpace();
                switch (vlSpClass) {
                    case VSPACE_NUM:
                        NumericType type = classifyNumeric("javaSprintf", nvValue);
                        switch (type) {
                            case OP_DECIMAL:
                                objVals.add(nvValue.getDecimal());
                                break;
                            case OP_INTEGER:
                                objVals.add(nvValue.getInteger());
                                break;
                            case OP_DOUBLE:
                                objVals.add(nvValue.getDouble());
                                break;
                            case OP_FLOAT:
                                objVals.add(nvValue.getFloat());
                                break;
                        }
                        break;
                    case VSPACE_DATE:
                    case VSPACE_DATETIME:
                        XMLGregorianCalendar gregorianCalendarValue = nvValue.getDateTime();
                        objVals.add(gregorianCalendarValue.toGregorianCalendar().getTime());
                        break;
                    case VSPACE_STRING:
                        objVals.add(nvValue.getString());
                        break;
                    case VSPACE_BOOLEAN:
                        objVals.add(nvValue.getBoolean());
                        break;
                    case VSPACE_LANG:
                        objVals.add(nvValue.getLang());
                        break;
                    default:
/*              These cases for the moment are not supported. We treat them all like strings.
                case VSPACE_NODE:
                case VSPACE_TIME:
                case VSPACE_G_DAY:
                case VSPACE_G_MONTH:
                case VSPACE_G_MONTHDAY:
                case VSPACE_G_YEAR:
                case VSPACE_G_YEARMONTH:
                case VSPACE_DURATION:
                case VSPACE_UNKNOWN:
*/
                        objVals.add(NodeFunctions.str(nvValue));
                        break;
                }
            }

            return NodeValue.makeString(String.format(formatForOutput,objVals.toArray()));

        } catch (IndexOutOfBoundsException ex) {
            throw new ExprEvalException("IndexOutOfBounds", ex);
        }
    }

    public static NodeValue strlen(NodeValue nvString) {
        Node n = NodeValueOps.checkAndGetStringLiteral("strlen", nvString);
        String str = n.getLiteralLexicalForm();
        int len = str.codePointCount(0, str.length());
        return NodeValue.makeInteger(len);
    }

    public static NodeValue strReplace(NodeValue nvStr, NodeValue nvPattern, NodeValue nvReplacement, NodeValue nvFlags) {
        String pat = NodeValueOps.checkAndGetStringLiteral("replace", nvPattern).getLiteralLexicalForm();
        String flagsStr = null;
        if ( nvFlags != null )
            flagsStr = NodeValueOps.checkAndGetStringLiteral("replace", nvFlags).getLiteralLexicalForm();
        return strReplace(nvStr, RegexEngine.makePattern("replace", pat, flagsStr), nvReplacement);
    }

    public static NodeValue strReplace(NodeValue nvStr, Pattern pattern, NodeValue nvReplacement) {
        String n = NodeValueOps.checkAndGetStringLiteral("replace", nvStr).getLiteralLexicalForm();
        String rep = NodeValueOps.checkAndGetStringLiteral("replace", nvReplacement).getLiteralLexicalForm();
        String x = replaceAll(pattern.matcher(n), rep);
        if ( x == null )
            // No replacement.
            return nvStr;
        if ( x.equals(n) )
            // No change - return original.
            return nvStr;
        return calcReturn(x, nvStr.asNode());
    }

    // Jena's replaceAll and xsd:func-replace differ in the handling of matching
    // an empty string.
    // Java:  ("", ".*", "x") --> "x" and ("notEmpty", ".*", "x") --> "xx"
    // F&O: [err:FORX0003] (in F&O, a global error; SPARQL does not have global execution errors)
    // http://www.w3.org/TR/xpath-functions/#func-replace
    // ARQ

    private static String replaceAll(Matcher matcher, String rep) {
        try {
            StringBuilder sb = null;   // Delay until needed
            while(matcher.find()) {
                if ( sb == null )
                    sb = new StringBuilder();
                else {
                    // Do one match of zerolength string otherwise filter out.
                    if (matcher.start() == matcher.end() )
                        continue;
                }
                matcher.appendReplacement(sb, rep);
            }
            if ( sb == null )
                return null;
            matcher.appendTail(sb);
            return sb.toString();
        } catch (IndexOutOfBoundsException ex) {
            throw new ExprEvalException("IndexOutOfBounds", ex);
        }
    }

    public static NodeValue strReplace(NodeValue nvStr, NodeValue nvPattern, NodeValue nvReplacement) {
        return strReplace(nvStr, nvPattern, nvReplacement, null);
    }

    public static NodeValue substring(NodeValue v1, NodeValue v2) {
        return substring(v1, v2, null);
    }

    public static NodeValue substring(NodeValue nvString, NodeValue nvStart, NodeValue nvLength) {
        Node n = NodeValueOps.checkAndGetStringLiteral("substring", nvString);
        RDFDatatype dt = n.getLiteralDatatype();
        // XSD F&O:
        try {
            String string = n.getLiteralLexicalForm();

            // Length in code points.
            int cpLength = string.codePointCount(0,  string.length());

            // Arguments.
            int start = intValueStr(nvStart, cpLength + 1);
            int length;

            if ( nvLength != null )
                length = intValueStr(nvLength, 0);
            else
                length = cpLength;

            // Evaluation.

            if ( string.isEmpty() )
                return nvString;

            // Working in codepoints indexes at this point

            // Includes negative start.
            int finish = start + length;

            // F&O strings are one-based; convert to java, 0 based.
            // Adjust to zero-offset, and ensure in-bounds -  still in codepoint indexes.
            // java needs indexes in-bounds.
            start--;
            finish--;
            if ( start < 0 )
                start = 0;
            if ( finish > cpLength )
                finish = cpLength; // Java index must be within bounds.
            if ( finish < start )
                finish = start;
            if ( finish < 0 )
                finish = 0;

            // Convert to UTF-16 code units to index values for the string.substring
            int xs = codePointToStringIndex(string, start, cpLength);
            int xf = codePointToStringIndex(string, finish, cpLength);

            String lex2 = string.substring(xs, xf);

            return calcReturn(lex2, n);
        } catch (IndexOutOfBoundsException ex) {
            throw new ExprEvalException("IndexOutOfBounds", ex);
        }
    }

    /** Convert zero-based codepoint to zero-based Java string index in-bounds.*/
    private static int codePointToStringIndex(String string, int index, int cpLength) {
        if ( index < 0 )
            return 0;

        return (index > cpLength)
                    ? string.length()
                    : string.offsetByCodePoints(0, index);
    }

    // NaN, float and double.
    private static int intValueStr(NodeValue nv, int valueNan) {
        if ( nv.isInteger() )
            return nv.getInteger().intValue();
        if ( nv.isDecimal() )
            return (int)Math.round(nv.getDecimal().doubleValue());

        if ( nv.isFloat() ) {
            float f = nv.getFloat();
            if ( Float.isNaN(f) )
                return valueNan;
            return Math.round(f);
        }
        if ( nv.isDouble() ) {
            double d = nv.getDouble();
            if ( Double.isNaN(d) )
                return valueNan;
            return (int)Math.round(d);
        }
        throw new ExprEvalException("Not a number:" + nv);
    }

    public static NodeValue strContains(NodeValue string, NodeValue match) {
        NodeValueOps.checkTwoArgumentStringLiterals("contains", string, match);
        String lex1 = string.asNode().getLiteralLexicalForm();
        String lex2 = match.asNode().getLiteralLexicalForm();
        boolean x = StrUtils.contains(lex1, lex2);
        return NodeValue.booleanReturn(x);
    }

    public static NodeValue strStartsWith(NodeValue string, NodeValue match) {
        NodeValueOps.checkTwoArgumentStringLiterals("strStarts", string, match);
        String lex1 = string.asNode().getLiteralLexicalForm();
        String lex2 = match.asNode().getLiteralLexicalForm();
        return NodeValue.booleanReturn(lex1.startsWith(lex2));
    }

    public static NodeValue strEndsWith(NodeValue string, NodeValue match) {
        NodeValueOps.checkTwoArgumentStringLiterals("strEnds", string, match);
        String lex1 = string.asNode().getLiteralLexicalForm();
        String lex2 = match.asNode().getLiteralLexicalForm();
        return NodeValue.booleanReturn(lex1.endsWith(lex2));
    }

    /** Build a NodeValue with lexical form, and same language and datatype as the Node argument */
    private static NodeValue calcReturn(String result, Node arg) {
        Node n2 = NodeFactory.createLiteral(result, arg.getLiteralLanguage(), arg.getLiteralDatatype());
        return NodeValue.makeNode(n2);
    }

    public static NodeValue strBefore(NodeValue string, NodeValue match) {
        NodeValueOps.checkTwoArgumentStringLiterals("strBefore", string, match);
        String lex1 = string.asNode().getLiteralLexicalForm();
        String lex2 = match.asNode().getLiteralLexicalForm();
        Node mainArg = string.asNode();

        if ( lex2.length() == 0 )
            return calcReturn("", mainArg);

        int i = lex1.indexOf(lex2);
        if ( i < 0 )
            return NodeValue.nvEmptyString;

        String s = lex1.substring(0, i);
        return calcReturn(s, string.asNode());
    }

    public static NodeValue strAfter(NodeValue string, NodeValue match) {
        NodeValueOps.checkTwoArgumentStringLiterals("strAfter", string, match);
        String lex1 = string.asNode().getLiteralLexicalForm();
        String lex2 = match.asNode().getLiteralLexicalForm();
        Node mainArg = string.asNode();

        if ( lex2.length() == 0 )
            return calcReturn(lex1, mainArg);

        int i = lex1.indexOf(lex2);
        if ( i < 0 )
            return NodeValue.nvEmptyString;
        i += lex2.length();
        String s = lex1.substring(i);
        return calcReturn(s, string.asNode());
    }

    public static NodeValue strLowerCase(NodeValue string) {
        Node n = NodeValueOps.checkAndGetStringLiteral("lcase", string);
        String lex = n.getLiteralLexicalForm();
        String lex2 = lex.toLowerCase();
        return calcReturn(lex2, string.asNode());
    }

    public static NodeValue strUpperCase(NodeValue string) {
        Node n = NodeValueOps.checkAndGetStringLiteral("ucase", string);
        String lex = n.getLiteralLexicalForm();
        String lex2 = lex.toUpperCase();
        return calcReturn(lex2, string.asNode());
    }

    public static NodeValue strEncodeForURI(NodeValue v) {
        Node n = v.asNode();
        if ( !n.isLiteral() )
            throw new ExprEvalException("Not a literal");
        if ( ! Util.isSimpleString(n) && ! Util.isLangString(n) )
            throw new ExprEvalException("Not a string literal");

        String str = n.getLiteralLexicalForm();
        String encStr = IRILib.encodeUriComponent(str);
        encStr = IRILib.encodeNonASCII(encStr);

        return NodeValue.makeString(encStr);
    }

    /** {@literal F&O} fn:concat (implicit cast to strings). */
    public static NodeValue fnConcat(List<NodeValue> args) {
        StringBuilder sb = new StringBuilder();

        for (NodeValue arg : args) {
            String x = arg.asString();
            sb.append(x);
        }
        return NodeValue.makeString(sb.toString());
    }

    /** SPARQL CONCAT (no implicit casts to strings) */
    public static NodeValue strConcat(List<NodeValue> args) {
        // Step 1 : Choose type.
        // One lang tag -> that lang tag
        String lang = null;
        boolean mixedLang = false;
        boolean xsdString = false;
        boolean simpleLiteral = false;

        StringBuilder sb = new StringBuilder();

        for (NodeValue nv : args) {
            Node n = NodeValueOps.checkAndGetStringLiteral("CONCAT", nv);
            String lang1 = n.getLiteralLanguage();
            if ( !lang1.equals("") ) {
                if ( lang != null && !lang1.equals(lang) )
                    // throw new
                    // ExprEvalException("CONCAT: Mixed language tags: "+args);
                    mixedLang = true;
                lang = lang1;
            } else if ( n.getLiteralDatatype() != null )
                xsdString = true;
            else
                simpleLiteral = true;

            sb.append(n.getLiteralLexicalForm());
        }

        if ( mixedLang )
            return NodeValue.makeString(sb.toString());

        // Must be all one lang.
        if ( lang != null ) {
            if ( !xsdString && !simpleLiteral )
                return NodeValue.makeNode(sb.toString(), lang, (String)null);
            else
                // Lang and one or more of xsd:string or simpleLiteral.
                return NodeValue.makeString(sb.toString());
        }

        if ( simpleLiteral && xsdString )
            return NodeValue.makeString(sb.toString());
        // All xsdString
        if ( xsdString )
            return NodeValue.makeNode(sb.toString(), XSDDatatype.XSDstring);
        if ( simpleLiteral )
            return NodeValue.makeString(sb.toString());

        // No types - i.e. no arguments
        return NodeValue.makeString(sb.toString());
    }

    /** fn:normalizeSpace */
    public static NodeValue strNormalizeSpace(NodeValue v){
        String str = v.asString();
        if(str == "" )
            return NodeValue.nvEmptyString;
        // is it possible that str is null?
        str = str.trim().replaceAll("\\s+"," ");
        return NodeValue.makeString(str);
    }

    public static NodeValue strNormalizeUnicode(NodeValue v1, NodeValue v2) {
        String normalizationFormStr = "nfc";
        if(v2 != null)
            normalizationFormStr = v2.asNode().getLiteralLexicalForm().toLowerCase();

        String inputString = v1.asString();
        if(normalizationFormStr.isEmpty())
            return NodeValue.makeString(inputString);
        // is it possible that normalizationFormStr is null?

        Normalizer.Form normalizationForm = Normalizer.Form.NFC;
        switch(normalizationFormStr)
        {
            case "nfd":
                normalizationForm = Normalizer.Form.NFD;
                break;
            case "nfkd":
                normalizationForm = Normalizer.Form.NFKD;
                break;
            case "nfkc":
                normalizationForm = Normalizer.Form.NFKC;
                break;
            case "nfc":
                normalizationForm = Normalizer.Form.NFC;
                break;
            case "fully-normalized":
                // not fully understood how to implement the fully-normalized normalization form.
                throw new ExprEvalTypeException("The fully-normalized normalization form is not supported.");
            default:
                throw new ExprEvalTypeException("Unrecognized normalization form "+normalizationFormStr+". Supported normalization forms: NFC,NFD,NFKD and NFKC.");
        }

        return NodeValue.makeString(Normalizer.normalize(inputString,normalizationForm));
    }

    public static NumericType classifyNumeric(String fName, NodeValue nv1, NodeValue nv2) {
        if ( !nv1.isNumber() )
            throw new ExprEvalTypeException("Not a number (first arg to " + fName + "): " + nv1);
        if ( !nv2.isNumber() )
            throw new ExprEvalTypeException("Not a number (second arg to " + fName + "): " + nv2);

        if ( nv1.isInteger() ) {
            if ( nv2.isInteger() )
                return OP_INTEGER;
            if ( nv2.isDecimal() )
                return OP_DECIMAL;
            if ( nv2.isFloat() )
                return OP_FLOAT;
            if ( nv2.isDouble() )
                return OP_DOUBLE;
            throw new ARQInternalErrorException("Numeric op unrecognized (second arg to " + fName + "): " + nv2);
        }

        if ( nv1.isDecimal() ) {
            if ( nv2.isDecimal() )
                return OP_DECIMAL;
            if ( nv2.isFloat() )
                return OP_FLOAT;
            if ( nv2.isDouble() )
                return OP_DOUBLE;
            throw new ARQInternalErrorException("Numeric op unrecognized (second arg to " + fName + "): " + nv2);
        }

        if ( nv1.isFloat() ) {
            if ( nv2.isFloat() )
                return OP_FLOAT;
            if ( nv2.isDouble() )
                return OP_DOUBLE;
            throw new ARQInternalErrorException("Numeric op unrecognized (second arg to " + fName + "): " + nv2);
        }

        if ( nv1.isDouble() ) {
            if ( nv2.isDouble() )
                return OP_DOUBLE;
            throw new ARQInternalErrorException("Numeric op unrecognized (second arg to " + fName + "): " + nv2);
        }

        throw new ARQInternalErrorException("Numeric op unrecognized (first arg to " + fName + "): " + nv1);
    }

    public static NumericType classifyNumeric(String fName, NodeValue nv) {
        if ( !nv.isNumber() )
            throw new ExprEvalTypeException("Not a number: (" + fName + ") " + nv);
        if ( nv.isInteger() )
            return OP_INTEGER;
        if ( nv.isDecimal() )
            return OP_DECIMAL;
        if ( nv.isFloat() )
            return OP_FLOAT;
        if ( nv.isDouble() )
            return OP_DOUBLE;
        throw new ARQInternalErrorException("Numeric op unrecognized (" + fName + "): " + nv);
    }

    private static Set<XSDDatatype> integerSubTypes = Set.of
            (XSDDatatype.XSDint,
             XSDDatatype.XSDlong,
             XSDDatatype.XSDshort,
             XSDDatatype.XSDbyte,
             XSDDatatype.XSDunsignedByte,
             XSDDatatype.XSDunsignedShort,
             XSDDatatype.XSDunsignedInt,
             XSDDatatype.XSDunsignedLong,
             XSDDatatype.XSDinteger,
             XSDDatatype.XSDnonPositiveInteger,
             XSDDatatype.XSDnonNegativeInteger,
             XSDDatatype.XSDpositiveInteger,
             XSDDatatype.XSDnegativeInteger
            );

    public static boolean isNumericDatatype(XSDDatatype xsdDatatype) {
        if ( XSDDatatype.XSDfloat.equals(xsdDatatype) )
            return true;
        if ( XSDDatatype.XSDdouble.equals(xsdDatatype) )
            return true;
        return isDecimalDatatype(xsdDatatype);
    }

    public static boolean isNumeric(Node node) {
        if ( ! node.isLiteral() )
            return false;
        RDFDatatype rdfDT = node.getLiteralDatatype();
        if ( ! ( rdfDT instanceof XSDDatatype ) )
            return false;
        return isNumericDatatype((XSDDatatype)rdfDT);
    }

    public static boolean isDecimalDatatype(XSDDatatype xsdDatatype) {
        if ( XSDDatatype.XSDdecimal.equals(xsdDatatype) )
            return true;
        return isIntegerDatatype(xsdDatatype);
    }

    public static boolean isIntegerDatatype(XSDDatatype xsdDatatype) {
        return integerSubTypes.contains(xsdDatatype);
    }

    private static Set<XSDDatatype> temporalDatatypes = Set.of(
             XSDDatatype.XSDdateTime,
             XSDDatatype.XSDtime,
             XSDDatatype.XSDdate,
             XSDDatatype.XSDgYear,
             XSDDatatype.XSDgYearMonth,
             XSDDatatype.XSDgMonth,
             XSDDatatype.XSDgMonthDay,
             XSDDatatype.XSDgDay
            );

    public static boolean isTemporalDatatype(XSDDatatype datatype) {
        return temporalDatatypes.contains(datatype);
    }

    public static boolean isDurationDatatype(XSDDatatype datatype) {
        return
            datatype.equals(XSDDatatype.XSDduration) ||
            datatype.equals(XSDDatatype.XSDyearMonthDuration) ||
            datatype.equals(XSDDatatype.XSDdayTimeDuration );
    }

    public static boolean isBinaryDatatype(XSDDatatype datatype) {
        return datatype.equals(XSDDatatype.XSDhexBinary) || datatype.equals(XSDDatatype.XSDbase64Binary);
    }


    // --------------------------------
    // Comparisons operations
    // Do not confuse with sameValueAs/notSamevalueAs

    private static int calcReturn(int x) {
        if ( x < 0 )
            return Expr.CMP_LESS;
        if ( x > 0 )
            return Expr.CMP_GREATER;
        return Expr.CMP_EQUAL;
    }

    public static int compareNumeric(NodeValue nv1, NodeValue nv2) {
        NumericType opType = classifyNumeric("compareNumeric", nv1, nv2);

        switch (opType) {
            case OP_INTEGER :
                return calcReturn(nv1.getInteger().compareTo(nv2.getInteger()));
            case OP_DECIMAL :
                return calcReturn(nv1.getDecimal().compareTo(nv2.getDecimal()));
            case OP_FLOAT :
                return calcReturn(Float.compare(nv1.getFloat(), nv2.getFloat()));
            case OP_DOUBLE :
                return calcReturn(Double.compare(nv1.getDouble(), nv2.getDouble()));
            default :
                throw new ARQInternalErrorException("Unrecognized numeric operation : (" + nv1 + " ," + nv2 + ")");
        }
    }

    // --------------------------------
    // Functions on strings
    // http://www.w3.org/TR/xpath-functions/#d1e2222
    // http://www.w3.org/TR/xpath-functions/#substring.functions

    // String operations
    //  stringCompare = fn:compare
    //  fn:length
    //  fn:string-concat
    //  fn:substring
    // langMatch

    public static int compareString(NodeValue nv1, NodeValue nv2) {
        return calcReturn(nv1.getString().compareTo(nv2.getString()));
    }

    // --------------------------------
    // Date/DateTime operations
    // works for dates as well because they are implemented as dateTimes on their start point.
    // The implicit timezone is fixed as UTC (Z, +00:00)
    // because we're on the web, locale makes less sense.
    // https://www.w3.org/TR/xpath-functions-3/#comp.datetime

    public static int compareDateTime(NodeValue nv1, NodeValue nv2) {
        // XSD Datatypes defines a partial order on dateTimes when comparing with
        // and without timezone => compareXSDDateTime
        // F&O defines a total order by applying the context-dependent implicit
        // timezone => compareDateTimeFO
        //
        // "Comparison operators on xs:date, xs:gYearMonth and xs:gYear compare their
        // starting instants. These xs:dateTime values are calculated as described
        // below."
       if ( SystemARQ.StrictDateTimeFO )
            return compareDateTimeFO(nv1, nv2);
        return compareDateTimeXSD(nv1, nv2);
    }

    /** Compare two date/times by XSD rules (dateTimes, one with and one without timezone can be indeterminate) */
    public static int compareDateTimeXSD(NodeValue nv1, NodeValue nv2) {
        XMLGregorianCalendar dt1 = getXMLGregorianCalendarXSD(nv1);
        XMLGregorianCalendar dt2 = getXMLGregorianCalendarXSD(nv2);
        int x = compareDateTime(dt1, dt2);
        return x;
    }

    /**
     * Strict {@literal F&O} handling of compare date(times).
     * But that means applying the "local" timezone if there is no TZ.
     * The data may have come from different timezones to the query.
     * We use a fixed locale timezone of UTC/00:00.
     */
    public static int compareDateTimeFO(NodeValue nv1, NodeValue nv2) {
        XMLGregorianCalendar dt1 = getXMLGregorianCalendarFO(nv1);
        XMLGregorianCalendar dt2 = getXMLGregorianCalendarFO(nv2);
        int x = compareDateTime(dt1, dt2);
        return x;
    }

    /** Return a normalized XMLGregorianCalendar appropriate for F&O comparison using the XSD algorithm. */
    private static XMLGregorianCalendar getXMLGregorianCalendarFO(NodeValue nv) {
        // This is a copy.
        XMLGregorianCalendar dt = nv.getDateTime();
        if ( dt.getTimezone() == DatatypeConstants.FIELD_UNDEFINED )
            dt.setTimezone(implicitTimezoneMinutes());

        if ( nv.isDate()) {
            // Force time.
            dt.setHour(0);
            dt.setMinute(0);
            dt.setSecond(0);
            return dt;
        }
        if ( nv.isTime()) {
            if ( dt.getHour() == 24 )
                // Normalize "24:00:00"
                dt.setHour(0);
            return dt;
        }
        if ( nv.isDateTime() ) {
            if ( dt.getHour() == 24 ) {
                dt.setHour(0);
                dt.add(duration1day);
            }
            return dt;
        }
        return dt;
    }

    /** Compare date times, including "indeterminate" rather than applying locale timezone */
    public static int compareXSDDateTime(NodeValue nv1, NodeValue nv2) {
        XMLGregorianCalendar dt1 = getXMLGregorianCalendarXSD(nv1);
        XMLGregorianCalendar dt2 = getXMLGregorianCalendarXSD(nv2);

        // Returns codes are -1/0/1 but also 2 for "Indeterminate"
        // which occurs when one has a timezone and one does not
        // and they are less then 14 hours apart.

        // F&O has an "implicit timezone" - this code implements the XMLSchema
        // compare algorithm.

        int x = dt1.compare(dt2);
        return convertComparison(x);
    }


    /** Return a XMLGregorianCalendar appropriate for XSD comparision */
    private static XMLGregorianCalendar getXMLGregorianCalendarXSD(NodeValue nv) {
        XMLGregorianCalendar dt = nv.getDateTime();
        if ( nv.isTime()) {
            if ( dt.getHour() == 24 )
                // Normalize "24:00:00"
                dt.setHour(0);
            return dt;
        }
        if ( nv.isDateTime() ) {
            if ( dt.getHour() == 24 ) {
                dt.setHour(0);
                dt.add(duration1day);
            }
            return dt;
        }
        return dt;
    }

    /** Compare date times, after fixups for XSD or FO. */
    private static int compareDateTime(XMLGregorianCalendar dt1, XMLGregorianCalendar dt2) {
        // Returns codes are -1/0/1 but also 2 for "Indeterminate"
        // which occurs when one has a timezone and one does not
        // and they are less then 14 hours apart.

        // F&O has an "implicit timezone" - this code implements the XMLSchema
        // compare algorithm.

        int x = dt1.compare(dt2);
        return convertComparison(x);
    }

    private static int convertComparison(int x) {
        if ( x == DatatypeConstants.EQUAL )
            return Expr.CMP_EQUAL;
        if ( x == DatatypeConstants.LESSER )
            return Expr.CMP_LESS;
        if ( x == DatatypeConstants.GREATER )
            return Expr.CMP_GREATER;
        if ( x == DatatypeConstants.INDETERMINATE )
            return Expr.CMP_INDETERMINATE;
        throw new ARQInternalErrorException("Unexpected return from XSDDuration.compare: " + x);
    }

    // --------------------------------
    // Boolean operations

    /* Logical OR and AND is special with respect to handling errors truth table.
     * AND they take effective boolean values, not boolean
     *
    A       B   |   NOT A   A && B  A || B
    -------------------------------------
    E       E   |   E       E       E
    E       T   |   E       E       T
    E       F   |   E       F       E
    T       E   |   F       E       T
    T       T   |   F       T       T
    T       F   |   F       F       T
    F       E   |   T       F       E
    F       T   |   T       F       T
    F       F   |   T       F       F
    */

    // Not possible because of error masking.
    // public static NodeValue logicalOr(NodeValue x, NodeValue y)
    // public static NodeValue logicalAnd(NodeValue x, NodeValue y)

    public static int compareBoolean(NodeValue nv1, NodeValue nv2) {
        boolean b1 = nv1.getBoolean();
        boolean b2 = nv2.getBoolean();
        if ( b1 == b2 )
            return Expr.CMP_EQUAL;

        if ( !b1 && b2 )
            return Expr.CMP_LESS;
        if ( b1 && !b2 )
            return Expr.CMP_GREATER;
        throw new ARQInternalErrorException("Weird boolean comparison: " + nv1 + ", " + nv2);
    }

    /**
     * Get the timezone in XSD timezone format (e.g. "Z" or "+01:00").
     * Assumes the NodeValue is of suitable datatype.
     */
    private static String tzStrFromNV(NodeValue nv) {
        DateTimeStruct dts = parseAnyDT(nv);
        if ( dts == null )
            return "";
        String tzStr = dts.timezone;
        if ( tzStr == null )
            tzStr = "";
        return tzStr;
    }

    /**
     * Cast a NodeValue to a date/time type (xsd dateTime, date, time, g*) according to {@literal F&O}
     * <a href="http://www.w3.org/TR/xpath-functions/#casting-to-datetimes">17.1.5 Casting to date and time types</a>
     * Throws an exception on incorrect case.
     *
     * @throws ExprEvalTypeException
     */
    public static NodeValue dateTimeCast(NodeValue nv, XSDDatatype xsd) {
        if ( nv.isString() ) {
            String s = nv.getString();
            if ( ! xsd.isValid(s) )
                throw new ExprEvalTypeException("Invalid lexical form: '"+s+"' for "+xsd.getURI());
            return NodeValue.makeNode(s, xsd);
        }

        if ( !nv.hasDateTime() )
            throw new ExprEvalTypeException("Not a date/time type: " + nv);

        XMLGregorianCalendar xsdDT = nv.getDateTime();

        if ( XSDDatatype.XSDdateTime.equals(xsd) ) {
            // ==> DateTime
            if ( nv.isDateTime() )
                return nv;
            if ( !nv.isDate() )
                throw new ExprEvalTypeException("Can't cast to XSD:dateTime: " + nv);
            // DateTime with time 00:00:00 ... and timezone, if any
            String tzStr = tzStrFromNV(nv);
            String x = String.format("%04d-%02d-%02dT00:00:00%s", xsdDT.getYear(), xsdDT.getMonth(), xsdDT.getDay(),
                                     tzStr);
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDdate.equals(xsd) ) {
            // ==> Date
            if ( nv.isDate() )
                return nv;
            if ( !nv.isDateTime() )
                throw new ExprEvalTypeException("Can't cast to XSD:date: " + nv);
            // Timezone
            String tzStr = tzStrFromNV(nv);
            String x = String.format("%04d-%02d-%02d%s", xsdDT.getYear(), xsdDT.getMonth(), xsdDT.getDay(), tzStr);
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDtime.equals(xsd) ) {
            // ==> time
            if ( nv.isTime() )
                return nv;
            if ( !nv.isDateTime() )
                throw new ExprEvalTypeException("Can't cast to XSD:time: " + nv);
            // Careful formatting

            DateTimeStruct dts = parseAnyDT(nv);
            if ( dts.timezone == null )
                dts.timezone = "";
            String x = String.format("%s:%s:%s%s", dts.hour, dts.minute, dts.second, dts.timezone);
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDgYear.equals(xsd) ) {
            // ==> Year
            if ( nv.isGYear() )
                return nv;
            if ( !nv.isDateTime() && !nv.isDate() )
                throw new ExprEvalTypeException("Can't cast to XSD:gYear: " + nv);
            String x = String.format("%04d", xsdDT.getYear());
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDgYearMonth.equals(xsd) ) {
            // ==> YearMonth
            if ( nv.isGYearMonth() )
                return nv;
            if ( !nv.isDateTime() && !nv.isDate() )
                throw new ExprEvalTypeException("Can't cast to XSD:gYearMonth: " + nv);
            String x = String.format("%04d-%02d", xsdDT.getYear(), xsdDT.getMonth());
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDgMonth.equals(xsd) ) {
            // ==> Month
            if ( nv.isGMonth() )
                return nv;
            if ( !nv.isDateTime() && !nv.isDate() )
                throw new ExprEvalTypeException("Can't cast to XSD:gMonth: " + nv);
            String x = String.format("--%02d", xsdDT.getMonth());
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDgMonthDay.equals(xsd) ) {
            // ==> MonthDay
            if ( nv.isGMonthDay() )
                return nv;
            if ( !nv.isDateTime() && !nv.isDate() )
                throw new ExprEvalTypeException("Can't cast to XSD:gMonthDay: " + nv);
            String x = String.format("--%02d-%02d", xsdDT.getMonth(), xsdDT.getDay());
            return NodeValue.makeNode(x, xsd);
        }

        if ( XSDDatatype.XSDgDay.equals(xsd) ) {
            // Day
            if ( nv.isGDay() )
                return nv;
            if ( !nv.isDateTime() && !nv.isDate() )
                throw new ExprEvalTypeException("Can't cast to XSD:gDay: " + nv);
            String x = String.format("---%02d", xsdDT.getDay());
            return NodeValue.makeNode(x, xsd);
        }

        throw new ExprEvalTypeException("Can't case to <" + xsd.getURI() + ">: " + nv);
    }

    // Get years/months/days/hours/minutes/seconds from any type we understands.

    public static NodeValue getYear(NodeValue nv) {
        if ( nv.isDuration() ) return durGetYears(nv);
        return dtGetYear(nv);
    }

    public static NodeValue getMonth(NodeValue nv) {
        if ( nv.isDuration() ) return durGetMonths(nv);
        return dtGetMonth(nv);
    }

    public static NodeValue getDay(NodeValue nv) {
        if ( nv.isDuration() ) return XSDFuncOp.durGetDays(nv);
        return dtGetDay(nv);
    }

    public static NodeValue getHours(NodeValue nv) {
        if ( nv.isDuration() ) return XSDFuncOp.durGetHours(nv);
        return dtGetHours(nv);
    }

    public static NodeValue getMinutes(NodeValue nv) {
        if ( nv.isDuration() ) return XSDFuncOp.durGetMinutes(nv);
        return dtGetMinutes(nv);
    }

    public static NodeValue getSeconds(NodeValue nv) {
        if ( nv.isDuration() ) return XSDFuncOp.durGetSeconds(nv);
        return dtGetSeconds(nv);
    }

    /** Create an xsd:dateTime from an xsd:date and an xsd:time. */
    public static NodeValue dtDateTime(NodeValue nv1, NodeValue nv2) {
        if ( ! nv1.isDate() )
            throw new ExprEvalException("fn:dateTime: arg1: Not an xsd:date: "+nv1);
        if ( ! nv2.isTime() )
            throw new ExprEvalException("fn:dateTime: arg2: Not an xsd:time: "+nv2);
        String lex1 = nv1.asNode().getLiteralLexicalForm();
        String lex2 = nv2.asNode().getLiteralLexicalForm();

        DateTimeStruct dts1 = DateTimeStruct.parseDate(lex1);
        DateTimeStruct dts2 = DateTimeStruct.parseTime(lex2);

        if ( dts1.hasTimezone() && dts2.hasTimezone() ) {
            if ( ! Objects.equals(dts1.timezone, dts2.timezone) )
                throw new ExprEvalException("fn:dateTime: Two different timezones: ("+nv1+", "+nv2+")");
        }

        // Merge the date into the time.  There are zero or one timezones, or two the same by this point.
        dts2.year = dts1.year;
        dts2.month = dts1.month;
        dts2.day = dts1.day;
        dts2.timezone = ( dts1.timezone != null ) ? dts1.timezone : dts2.timezone;
        String lex = dts2.toString();
        return NodeValue.makeDateTime(lex);
    }

    // Accessors: datetime, date, Gregorian.
    public static NodeValue dtGetYear(NodeValue nv) {
        if ( nv.isDateTime() || nv.isDate() || nv.isGYear() || nv.isGYearMonth() ) {
            DateTimeStruct dts = parseAnyDT(nv);
            if ( dts.neg != null )
                return NodeValue.makeNode("-"+dts.year, XSDDatatype.XSDinteger);
            return NodeValue.makeNode(dts.year, XSDDatatype.XSDinteger);
        }
        throw new ExprEvalException("Not a year datatype");
    }

    public static NodeValue dtGetMonth(NodeValue nv) {
        if ( nv.isDateTime() || nv.isDate() || nv.isGYearMonth() || nv.isGMonth() || nv.isGMonthDay() ) {
            DateTimeStruct dts = parseAnyDT(nv);
            return NodeValue.makeNode(dts.month, XSDDatatype.XSDinteger);
        }
        throw new ExprEvalException("Not a month datatype");
    }

    public static NodeValue dtGetDay(NodeValue nv) {
        if ( nv.isDateTime() || nv.isDate() || nv.isGMonthDay() || nv.isGDay() ) {
            DateTimeStruct dts = parseAnyDT(nv);
            return NodeValue.makeNode(dts.day, XSDDatatype.XSDinteger);
        }
        throw new ExprEvalException("Not a day datatype");
    }

    private static DateTimeStruct parseAnyDT(NodeValue nv) {
        String lex = nv.asNode().getLiteralLexicalForm();
        if ( nv.isDateTime() )
            return DateTimeStruct.parseDateTime(lex);
        if ( nv.isDate() )
            return DateTimeStruct.parseDate(lex);
        if ( nv.isGYear() )
            return DateTimeStruct.parseGYear(lex);
        if ( nv.isGYearMonth() )
            return DateTimeStruct.parseGYearMonth(lex);
        if ( nv.isGMonth() )
            return DateTimeStruct.parseGMonth(lex);
        if ( nv.isGMonthDay() )
            return DateTimeStruct.parseGMonthDay(lex);
        if ( nv.isGDay() )
            return DateTimeStruct.parseGDay(lex);
        if ( nv.isTime() )
            return DateTimeStruct.parseTime(lex);
        return null;
    }

    private static DateTimeStruct parseTime(NodeValue nv) {
        String lex = nv.asNode().getLiteralLexicalForm();
        if ( nv.isDateTime() )
            return DateTimeStruct.parseDateTime(lex);
        else if ( nv.isTime() )
            return DateTimeStruct.parseTime(lex);
        else
            throw new ExprEvalException("Not a datatype for time");
    }

    public static NodeValue dtGetHours(NodeValue nv) {
        DateTimeStruct dts = parseTime(nv);
        return NodeValue.makeNode(dts.hour, XSDDatatype.XSDinteger);
    }

    public static NodeValue dtGetMinutes(NodeValue nv) {
        DateTimeStruct dts = parseTime(nv);
        return NodeValue.makeNode(dts.minute, XSDDatatype.XSDinteger);
    }

    public static NodeValue dtGetSeconds(NodeValue nv) {
        DateTimeStruct dts = parseTime(nv);
        return NodeValue.makeNode(dts.second, XSDDatatype.XSDdecimal);
    }

    public static NodeValue dtGetTZ(NodeValue nv) {
        DateTimeStruct dts = parseAnyDT(nv);
        if ( dts == null )
            throw new ExprEvalException("Not a data/time value: " + nv);
        if ( dts.timezone == null )
            return NodeValue.nvEmptyString;
        return NodeValue.makeString(dts.timezone);
    }

    public static NodeValue dtGetTimezone(NodeValue nv) {
        DateTimeStruct dts = parseAnyDT(nv);
        if ( dts == null || dts.timezone == null )
            throw new ExprEvalException("Not a datatype with a timezone: " + nv);
        if ( "".equals(dts.timezone) )
            return null;
        if ( "Z".equals(dts.timezone) ) {
            Node n = NodeFactory.createLiteralDT("PT0S", NodeFactory.getType(XSDDatatype.XSD + "#dayTimeDuration"));
            return NodeValue.makeNode(n);
        }
        if ( "+00:00".equals(dts.timezone) ) {
            Node n = NodeFactory.createLiteralDT("PT0S", NodeFactory.getType(XSDDatatype.XSD + "#dayTimeDuration"));
            return NodeValue.makeNode(n);
        }
        if ( "-00:00".equals(dts.timezone) ) {
            Node n = NodeFactory.createLiteralDT("-PT0S", NodeFactory.getType(XSDDatatype.XSD + "#dayTimeDuration"));
            return NodeValue.makeNode(n);
        }

        String s = dts.timezone;
        int idx = 0;
        StringBuilder sb = new StringBuilder();
        if ( s.charAt(0) == '-' )
            sb.append('-');
        idx++; // Skip '-' or '+'
        sb.append("PT");
        digitsTwo(s, idx, sb, 'H');
        idx += 2;
        idx++; // The ":"
        digitsTwo(s, idx, sb, 'M');
        idx += 2;
        return NodeValue.makeNode(sb.toString(), null, XSDDatatype.XSD + "#dayTimeDuration");
    }

    private static void digitsTwo(String s, int idx, StringBuilder sb, char indicator) {
        if ( s.charAt(idx) == '0' ) {
            idx++;
            if ( s.charAt(idx) != '0' ) {
                sb.append(s.charAt(idx));
                sb.append(indicator);
            }
            idx++;
        } else {
            sb.append(s.charAt(idx));
            idx++;
            sb.append(s.charAt(idx));
            idx++;
            sb.append(indicator);
        }
    }

    public static boolean isYearMonth(Duration dur) {
        // Not dur.getXMLSchemaType()
        return (dur.isSet(YEARS) || dur.isSet(MONTHS)) && !dur.isSet(DAYS) && !dur.isSet(HOURS) && !dur.isSet(MINUTES)
               && !dur.isSet(SECONDS);
    }

    public static boolean isDayTime(Duration dur) {
        return !dur.isSet(YEARS) && !dur.isSet(MONTHS)
               && (dur.isSet(DAYS) || dur.isSet(HOURS) || dur.isSet(MINUTES) || dur.isSet(SECONDS));
    }

    // ---- Durations

    public static NodeValue durGetYears(NodeValue nv) {
        return accessDuration(nv, DatatypeConstants.YEARS);
    }

    public static NodeValue durGetMonths(NodeValue nv) {
        return accessDuration(nv, DatatypeConstants.MONTHS);
    }

    public static NodeValue durGetDays(NodeValue nv) {
        return accessDuration(nv, DatatypeConstants.DAYS);
    }

    public static NodeValue durGetHours(NodeValue nv) {
        return accessDuration(nv, DatatypeConstants.HOURS);
    }

    public static NodeValue durGetMinutes(NodeValue nv) {
        return accessDuration(nv, DatatypeConstants.MINUTES);
    }

    public static NodeValue durGetSeconds(NodeValue nv) {
        return accessDuration(nv, DatatypeConstants.SECONDS);
    }

    public static NodeValue durGetSign(NodeValue nv) {
        int x = nv.getDuration().getSign();
        return NodeValue.makeInteger(x);
    }

    private static NodeValue accessDuration(NodeValue nv, Field field) {
        Duration dur = nv.getDuration();
        // if ( ! nv.isDuration() )
        // throw new ExprEvalException("Not a duration: "+nv);
        Number x = dur.getField(field);
        if ( x == null ) {
            x =  field.equals(DatatypeConstants.SECONDS)
                ? BigDecimal.ZERO
                : BigInteger.ZERO;
        }

        if ( field.equals(DatatypeConstants.SECONDS) )
            return NodeValue.makeDecimal((BigDecimal)x);

        return NodeValue.makeInteger((BigInteger)x);
    }

    /** One day */
    private static Duration duration1day = NodeValue.xmlDatatypeFactory.newDuration(true, null, null, BigInteger.ONE, null, null, null);

    public static int compareDuration(NodeValue nv1, NodeValue nv2) {
        return compareDuration(nv1.getDuration(), nv2.getDuration());
    }

    private static int compareDuration(Duration duration1, Duration duration2) {
        // Returns codes are -1/0/1 but also 2 for "Indeterminate"
        // In F&O, the expression op:duration-equal(xs:duration("P1Y"), xs:duration("P365D")) returns false().
        return XSDDuration.durationCompare(duration1, duration2);
    }

    public static final String implicitTimezoneStr = "Z";
    private static final NodeValue implicitTimezone_ = NodeValue.makeNode("PT0S", XSDDatatype.XSDdayTimeDuration);

    // minutes are used for the timezone in XMLGregorianCalendar
    private static final int implicitTimezoneMinutes() { return 0; }

    /**
     * <a href="https://www.w3.org/TR/xpath-functions-3/#func-implicit-timezone">Implciit Timezone</a>
     * // https://www.w3.org/TR/xpath-functions-3/#comp.datetime
     */

    //fn:implicit-timezone() as xs:dayTimeDuration

    public static NodeValue implicitTimezone() {
        return implicitTimezone_;
    }

    /** Local timezone of the query engine: afn:system-timezone */
    public static NodeValue localSystemTimezone() {
        Duration dur = localSystemTimezoneDuration();
        String lex = dur.toString();
        NodeValue nv = NodeValue.makeNode(lex, XSDDatatype.XSDdayTimeDuration);
        return nv;
    }

    /** Local (query engine) timezone including DST */
    private static Duration localSystemTimezoneDuration() {
        ZonedDateTime zdt = ZonedDateTime.now();
        int tzDurationInSeconds = zdt.getOffset().getTotalSeconds();
        Duration dur = NodeFunctions.duration(tzDurationInSeconds);
        return dur;
    }

    /**
     * Adjust xsd:dateTime/xsd:date/xsd:time to a timezone.
     * This covers fn:adjust-dateTime-to-timezone, fn:adjust-date-to-timezone and fn:adjust-time-to-timezone.
     * via {@code ADJUST} ({@link E_AdjustToTimezone}).
     * If the second argument is null, use implicit timezone.
     * In Jena, the implicit timezone is fixed to UTC.
     */
    public static NodeValue adjustToTimezone(NodeValue nv1, NodeValue nv2){
        if(nv1 == null)
            return null;

        if(!nv1.isDateTime() && !nv1.isDate() && !nv1.isTime())
            throw new ExprEvalException("Not a valid date, datetime or time:"+nv1);

        XMLGregorianCalendar calValue = nv1.getDateTime();
        boolean hasTz = ( calValue.getTimezone() != DatatypeConstants.FIELD_UNDEFINED );
        int inputOffset = 0;
        if ( hasTz )
            inputOffset = calValue.getTimezone();

        // XSMLGregorianCalendar uses minutes for timezone.
        int tzOffsetMins = 0;
        if(nv2 != null){
            if(!nv2.isDuration()) {
                String nv2StrValue = nv2.getString();
                if(nv2StrValue.equals("")){
                    calValue.setTimezone(DatatypeConstants.FIELD_UNDEFINED);
                    if(nv1.isDateTime())
                        return NodeValue.makeDateTime(calValue);
                    else if(nv1.isTime())
                        return NodeValue.makeNode(calValue.toXMLFormat(), XSDDatatype.XSDtime);
                    else
                        return NodeValue.makeDate(calValue);
                }
                throw new ExprEvalException("Not a valid duration:" + nv2);
            }
            Duration tzDuration = nv2.getDuration();
            tzOffsetMins = tzDuration.getSign()*(tzDuration.getMinutes() + 60*tzDuration.getHours());
            if(tzDuration.getSeconds() > 0)
                throw new ExprEvalException("The timezone duration should be an integral number of minutes");
            int absTzOffset = java.lang.Math.abs(tzOffsetMins);
            if(absTzOffset > 14*60)
                throw new ExprEvalException("The timezone should be a duration between -PT14H and PT14H.");
        }
        else {
            tzOffsetMins = implicitTimezoneMinutes();
        }
        Duration durToAdd = NodeValue.xmlDatatypeFactory.newDurationDayTime((tzOffsetMins-inputOffset) > 0,0,0,java.lang.Math.abs(tzOffsetMins-inputOffset),0);
        if(hasTz)
            calValue.add(durToAdd);
        calValue.setTimezone(tzOffsetMins);
        if(nv1.isDateTime())
            return NodeValue.makeDateTime(calValue);
        else if(nv1.isTime())
            return NodeValue.makeNode(calValue.toXMLFormat(), XSDDatatype.XSDtime);
        else
            return NodeValue.makeDate(calValue);
    }

    /** fn:format-number
     *
     * The 3rd argument, if present, called decimal-format-name, is here a
     * IETF BCP 47 language tag string.
     */
    public static NodeValue formatNumber(NodeValue nv, NodeValue picture, NodeValue nvLocale) {
        if ( !nv.isNumber() )
            NodeValue.raise(new ExprEvalException("Not a number: " + nv));
        if ( !picture.isString() )
            NodeValue.raise(new ExprEvalException("Not a string: " + picture));
        if ( nvLocale != null && !nvLocale.isString() )
            NodeValue.raise(new ExprEvalException("Not a string: " + nvLocale));

        Locale locale = Locale.ROOT;
        if ( nvLocale != null )
            locale = Locale.forLanguageTag(nvLocale.asString());
        DecimalFormatSymbols dfs = DecimalFormatSymbols.getInstance(locale);

        NumberFormat formatter =
            (dfs == null )
                ? new DecimalFormat(picture.getString())
                : new DecimalFormat(picture.getString(), dfs);

        NumericType nt = XSDFuncOp.classifyNumeric("fn:formatNumber", nv);
        String s = null;
        switch(nt) {
            case OP_DECIMAL :
            case OP_DOUBLE :
            case OP_FLOAT :
                s = formatter.format(nv.getDouble());
                break;
            case OP_INTEGER :
                s = formatter.format(nv.getInteger().longValue());
                break;
            default :
                break;
        }
        return NodeValue.makeString(s);
    }
}
